Reading took a 2-0 lead into half-time after an own goal from Cardiff's Callum Paterson and a Modou Barrow strike gave the Royals the advantage.
Goals from Joe Bennett and Lee Tomlin late in the second half ensured Cardiff saved a point after dominating the second half.
Cardiff boss Neil Warnock was also sent off in the second half following a confrontation with the fourth official, leaving assistant coach Kevin Blackwell in charge for the last quarter of the game.
Royals take a two-goal lead in the opening 45
Both teams came into this game in good form. Reading were unbeaten in their last four league games, Cardiff having won their last four.
It was the away side who started the game the better, with Cardiff's attacking force looking to be a danger to the Royal's defence.
Cardiff winger Nathaniel Mendez-Laing almost put the Bluebirds ahead in the 13th minute. He forced a good save from Reading goalkeeper Vito Mannone after skipping past Paul McShane and firing the shot at Mannone's legs.
However, despite Cardiff's strong start, it was Reading who took the lead through a Paterson own goal.
Liam Kelly delivered a very dangerous corner to the near post, with Paterson only able to head the ball into his own net, putting Reading ahead in the 16th minute.
Cardiff responded well, with Junior Hoilett heading over from close range after he was put under pressure from McShane who looked to bundle the Canadian over in the box. No penalty.
From this point on, Reading had the upper-hand. They put pressure on the Bluebird's defence with Sone Aluko and Barrow really testing the away side's full-backs.
This pressure told as Reading increased their lead five minutes before half-time.
Another Kelly corner was partially cleared by Cardiff, but fell nicely for Barrow on the edge of the box. His shot deflected off Cardiff left-back Bennett and into the back of the net past Neil Etheridge in goal.
Warnock's men fight back to earn a point
Warnock's men started strongly after the half-time break, with Hoilett coming close to halving Reading's lead. The winger was found free in the area, and headed downwards towards goal, only to see his effort bounce over the bar.
Cardiff continued to press and almost got a goal back when Bennett was found on the edge of the box. However, he could only find row Z.
Cardiff's evening was dealt another blow in the 75th minute as manager Warnock was sent off by referee Steve Martin following a heated discussion with the fourth official.
However, it was Bennett who gave Cardiff a glimmer of hope in the 82nd minute, hitting a sweet volley on the edge of the box, which rocketed past Mannone in goal.
The game took another twist when Cardiff equalised in the 90th minute after Sol Bamba hit the bar with a header and Tomlin smashed the ball towards goal. The shot hit the bar and came out, but the referee ruled that the ball had crossed the line, awarding Cardiff the goal.
Reading came close to winning it late on, with McShane hitting the post with a header.
The point keeps Cardiff in second place in the Championship, with the Bluebirds sitting four points above third placed Bristol City. As for Reading, they move up to 14th, level on points with Brentford who are in 13th.